Defining the regions of the brain displaying the neuropathological lesions that cause Alzheimer's disease (AD) will facilitate deeper investigation into their pathophysiology. In addition, this would allow the effects of AD treatment to be specifically monitored in those regions. Cognitive decline in AD begins with failings of episodic memory and spatial orientation in patients with very mild AD. Clinical and experimental data show that the brain regions primarily involved in memory impairment early in AD are the hippocampus and the medial temporal lobe. Is it possible to prevent the development of pathophysiology in these regions? The neuroprotective effect of cholinesterase inhibitors has been demonstrated in a number of different models, including protection of cortical neurons in models of oxygen-glucose deprivation and glutamate-induced toxicity, and protection against the effects of hippocampal mitochondrial dysfunction in transgenic mouse models of AD. These preclinical data are supported by extensive clinical data indicating that maximum benefit is gained through early initiation of treatment with donepezil and suggest that the benefits afforded by donepezil may extend beyond those of a purely symptomatic treatment.